1. Field of the Invention
The present invention relates generally to fluid flow control devices. More particularly, the invention concerns a safety device for use in beverage distribution systems which positively prevents overpressurization of the beverage containers forming a part of the distribution systems.
2. Discussion of the Prior Art
In beverage distribution systems and particularly those used for beer, a pressure source is usually connected to a manifolding subsystem which is in turn connected to one or more kegs of beer through a tapping mechanism. The tapping mechanism permits the dispensing of beer from the keg under the pressure provided from the source. Safety devices have been employed in beverage installations of this kind to control the amount of pressure delivered to the keg. Otherwise, should a failure occur somewhere upstream of the keg tapping mechanism, the keg itself may become overpressurized to such an extent that it could very well explode or at least blow portions of the keg tapping mechanism with such force as to cause catastrophic consequences to those in the area of the keg. Safety devices used for this purpose have typically been mechanically adjustable and employed moving mechanical devices which are subject to frequent failure and blockage.
For adjustable safety devices the mostcommon technique has been the use of a spring bias release valve with various adjusting devices. There have also been attempts to incorporate safety relief valves in the pressure reducing regulator to control pressure delivered from the source. Unfortunately, the use of these adjustable regulators allow even a well-intentioned operator to adjust the regulator in a manner which cancels the effect of any safety mechanism. For example, when the operator hears the hissing noise that occurs when gas pressure begins being vented from the safety relief valve, and, knowing that this involves a gas leakage, he may adjust the safety relief valve to stop the leakage. In doing so, the relief valve may be bottomed out completely invalidating its existence or use.
Other prior art approaches to the problem have included the installation of safety relief valves in the beverage container itself. This has not proved to be completely satisfactory. By installing the relief valve inside the beverage container, it is continually exposed to the beverage product being dispensed from that container. As these products are by their very nature sticky, they adversely affect the predictability of the valves with which the beverage comes in contact. In other words, as the sticky beverage material permeates the interstices of the valve mechanism, elements of the mechanism may become adhered to one another to such an extent that it will not work properly, if at all.
With regard to the spring bias relief valve system generally used in the connection apparatus, they are also subject to the major disadvantage of their constant exposure to the beverage itself. As mentioned above, the beverage is sticky and as it dries, it forms a reasonably effective glue which causes the lifting or actuating pressure of the valve itself to vary widely. Because of this variation, the spring bias release system is one which is found to be unreliable and unsafe.
Another major disadvantage is that these safety valves are normally incorporated into some other component element of the dispensing system. They are usually employed with the coupler body of the coupler device which is used to interconnect the beverage container with the dispensing hoses and faucets. Because of the limitations in space and costs imposed on these systems, it is necessary that the safety system also be sufficiently small to work within the coupler. As a result of this size limitation, the safety valves may not provide an adequately large orifice through which to expel the excessive gases being applied from an overpressured or malfunctioning gas pressure regulator.
The pressure systems used with beverage distribution systems may require a source gas pressure of up to 1000 pounds per square inch. This, of course, varies substantially with temperature, but the normal pressure involved is usually around 800 pounds per square inch. If the reducing regulator on the gas cylinder should fail, allowing full bottle or source pressure to flow into the gas pressure feedline, the gas will achieve flow rates of on the order of 60 to 100 cubic feet per minute. The size of the expulsion orifice in the existing safety relief valves are so small that they will not achieve the same flow rate at the same source pressure. More importantly, the upper safe limit of the keg pressure, which is much lower than the source pressure, will achieve a limited flow rate of only 17 to 21 standard cubic feet per minute. In other words, if they are not glued shut by the beverage residue and they lift at the proper pressure, they will not provide sufficient flow rate to safely vent the system. Their proper actuation merely delays the explosive rupture of the beverage container some fraction of a second or perhaps two seconds at the most, depending on whether the container is completely filled or partially filled with the beverage at the time of failure.
Because the beverage containers are placed within coolers and other storage places, there is also always the possibility of a blockage of the safety valve. In fact, in some coolers, the six packs of beverage cans or bottles, packages of meat, vegetables and other products are frequently refrigerated in restaurant environments and placed on or adjacent these valve mechanisms in such a way that block or prevent their actuation.
One of the most effective devices ever devised to solve the prior art problems set forth herein is the device disclosed in U.S. Pat. No. 4,219,040 which issued to one of the co-inventors of the present invention. The device of the invention herein described represents a further improvement over the device of U.S. Pat. No. 4,219,040 in that the undesirable venting of the gas to atmosphere is prevented by means of a unique safety control valve which has been incorporated into the design of the unit.
In beverage dispensing systems, carbon dioxide and nitrogen are frequently used as the pressurizing source gases. With the device of U.S. Pat. No. 4,219,040 overpressurization of the system will causes the rupture disc of the device to fail satisfactorily preventing over pressurization of the beverage containers, but permitting the source gas to flow to atmosphere. In such a case, flow will continue until the gas source is depleted. Where gas generators or large volume pressure tanks are used, either singly or in series, to supply the source gas, substantial quantities of gas can be lost if the failure of the burst disc is not promptly discovered. This dumping of large volumes of gas can itself create a significant safety hazard. For example, when CO2 is used as the source gas, and the system is installed in a relatively small room, risks of asphyxiation or hypoxia become substantial. Even in larger rooms, since CO2 will sink to the floor, if a workman should fall and remain on the floor for any length of time, hypoxia can result causing death or serious injury to the workman. Additionally, where the safety device of U.S. Pat. No. 4,219,040 is incorporated into systems using other, more toxic source gases, dumping of the source gas to atmosphere can be even more catastrophic unless regular monitoring of the system takes place.
The device of the present invention uniquely overcomes all of the drawbacks of the prior art safety devices by providing a device which not only prevents overpressurization of the beverage container but also prevents dumping of the source gas to atmosphere in the event of overpressurization of the system.